Question

What point on the line y=9x+8 is closest to the origin

Answer 1

to find the point, find the location

realize that the shortest line that crosses through the origin and y=9x+8 is perpendicular to y=9x+8

perpendicular lines have slopes that multiply to get -1

y=9x+8 has a slope of 9

9*m=-1, m=-1/9

the slope of the mystery line is -1/9

since it passes through the origin, the y intercept is 0

y=(-1/9)x is the equation of the line from the point to the origin

find the intersection of this line and the original line

set them equal to each other

(-1/9)x=9x+8

multily both sides by 9

-x=81x+72

minus 81 both sides

-82x=72

divide both sides by -82

x=-36/41

find y

y=(-1/9)x

y=(-1/9)(-36/41)

y=4/41

the point is $(\frac{-36}{41},\frac{4}{41})$